Composite brake drum and method for producing same

ABSTRACT

A composite brake drum for use in a drum brake assembly includes a one-piece mounting flange and shell and a liner cast integrally in a shell portion thereof. The method for forming the composite brake drum of this invention includes the steps of: (a) providing a generally circular metal blank having an initial pilot hole inner diameter; (b) spin forming the metal blank to produce a one-piece brake drum component defining a center longitudinal axis and including a cylindrical shell having a squealer band which defines a squealer band outer diameter, a mounting flange extending radially inwardly from one end of the shell toward the center longitudinal axis, and an annular lip extending radially inwardly from an opposite end of the shell toward the center longitudinal axis, and wherein the shell, the flange, and the lip cooperate to define a cylindrical mold cavity; (c) subsequent to step (b), centrifugally casting a liner in situ within the mold cavity of the brake drum component to thereby produce the composite vehicle brake drum; and (d) subsequent to step (c), machining the initial pilot hole inner diameter to a final pilot hole inner diameter by locating off of the squealer band outer diameter.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. Ser. No. 09/253,984, now U.S.Pat. No. 6,196,363, filed on Jul. 20, 1998, which is acontinuation-in-part of U.S. Ser. No. 08/769,196 now U.S. Pat. No.5,782,324, filed Dec. 18, 1996, which claims the benefit of U.S.Provisional Application No. 60/009,425, filed Dec. 27, 1995.

BACKGROUND OF THE INVENTION

This invention relates in general to vehicle drum brake assemblies andin particular to an improved structure for a composite brake drum foruse in such a vehicle drum brake assembly and method for producing thesame.

Most vehicles are equipped with a brake system for slowing or stoppingmovement of the vehicle in a controlled manner. A typical brake systemincludes either a disc brake assembly or a drum brake assembly for eachof the wheels. The brake assemblies are typically actuated by hydraulicor pneumatic pressure generated by an operator of the vehicle depressinga foot pedal, pulling a hand lever, and the like. The structure andoperation of the brake assemblies, as well as the actuators therefor,are well known in the art.

FIG. 1 illustrates a prior art pneumatically actuated drum brakeassembly, indicated generally at 10, typically for use with a heavy dutytruck and trailer. As shown therein, the drum brake assembly 10 includesa backing plate 12 which is secured to a fixed, non-rotatable componentof the vehicle, such as the vehicle axle housing (not shown). A pair ofopposed arcuate brake shoes 14 (only one brake shoe 14 is illustrated)are supported on the backing plate 12 for selective movement relativethereto. Each of the brake shoes 14 has a friction pad 16 securedthereto.

The brake drum assembly 10 further includes a hollow cylindrical “heavyduty” composite brake drum 18 shown in prior art FIG. 2. The brake drum18 is disposed adjacent the backing plate 12 such that the brake shoes14 extend within an inner cylindrical braking surface 24A thereof. Toeffect braking action, the brake shoes 14 are moved outwardly apart fromone another such that the friction pads 16 frictionally engage thecylindrical braking surface 24A of the brake drum 18. Such frictionalengagement causes slowing or stopping of the rotational movement of thebrake drum 18 and, therefore, the wheel of the vehicle in a controlledmanner.

One or more actuating mechanisms are provided in the drum brake assembly10 for selectively moving the brake shoes 14 outwardly apart from oneanother into frictional engagement with the cylindrical braking surface24A of the brake drum 18. Usually, a pneumatically actuated servicebrake mechanism is provided for selectively actuating the drum brakeassembly 10 under normal is operating conditions. Typically, the servicebrake mechanism includes an air chamber device 26, a lever assembly 28,and a S-cam actuating mechanism 30. To actuate the service brake,pressurized air is supplied to the air chamber device 26 to actuate thelever assembly 28 which in turn rotates the S-cam actuating mechanism 30to move brake shoes 14 apart from one another into frictional engagementwith the cylindrical braking surface 24A of the brake drum 18. Amechanically actuated parking and emergency brake mechanism is alsousually provided for selectively actuating the drum brake assembly 10 ina similar manner.

FIG. 3 illustrates a typical sequence of steps for producing the brakedrum 18 shown in prior art FIGS. 1 and 2. First, referring to the lefthand side of FIG. 3, the steps involved in the process of forming ashell portion 22 and a liner portion 24 of the brake drum 18 areillustrated. Initially, in step 40, a flat sheet of suitable material,such as for example steel, is formed into a generally flat band having adesired profile, such as by a roll forming process. Next, in step 42,the opposed ends of the band are disposed adjacent one another andwelded together to form a hoop. In step 44, the hoop is expanded toproduce the shell portion 22 having a desired profile shown in FIG. 2.Following this, the liner portion 24 is cast in the shell portion 22,preferably by a centrifugally casting process in step 46. After this, instep 48, the shell portion 22 and the liner portion 24 are roughmachined.

Now, referring to the right hand side of FIG. 3, the steps involved inthe process of forming a mounting flange portion 20 of the brake drum18, and the steps involved in the process of forming the brake drum 18itself, are illustrated. In step 50, a flat sheet of suitable material,such as for example steel, is formed into a mounting flange blank, suchas by a stamping process. Following this, in step 52, the mountingflange blank is formed into the mounting flange portion 20 having adesired profile by a stamping process. A plurality of lug bolt mountingholes 20C (only one lug bolt mounting hole 20C being illustrated in FIG.2), can be simultaneously formed in the flange portion 20. As is known,lug bolts (not shown) extend through the lug bolt holes 20C to securethe brake drum 18 to a vehicle wheel (not shown) for rotation therewith.In step 54, an inner end 20A of the mounting flange portion 20 isdisposed adjacent an outer end 22B of the shell portion 22 and weldedtogether to join the shell portion 22 and the liner 24 portion to themounting flange portion 20. Next, a pilot hole 20B is formed in themounting flange portion 20 during step 56.

In step 58, the brake drum 18 is finish machined to predeterminedtolerances. Following this, the brake drum 18 is typically subjected toa balancing operation in step 60. In particular, one or more wheelbalance weights (not shown) are usually attached to an outer surface ofthe shell portion 22 by welding to produce the finished brake drum 18.Typically, the mounting flange 20 of the brake drum 18 defines agenerally constant mounting flange thickness T1, and the shell portion22 defines a generally constant shell thickness T2 which is less thanthe mounting flange thickness T1. Alternatively, the brake drum can be aheavy duty “full cast” brake drum, indicated generally at 32 in priorart FIG. 4. As shown therein the brake drum 32 includes an integralraised squealer band 34 provided on an outer surface thereof.

The composite brake drum 18 illustrated in FIGS. 1 and 2 is considerablylighter than the full cast brake drum 32 illustrated in FIG. 4. However,the full cast brake drum 32 can be produced using a simplermanufacturing process than the process used to produce the compositebrake drum 18. Also, each of the brake drums 18 and 32 typicallyincorporates a sufficient imbalance which renders them unsatisfactoryfor use on a vehicle without balancing. There are several known methodsfor correcting the imbalance of the brake drums 18 and 32. Typically,the composite brake drum 18 is balanced by welding balance weights tothe outer surface of the drum. While the full cast brake drum 32 can bebalanced in a similar manner, it can also be balanced according to themethods disclosed in U.S. Pat. No. 4,986,149 to Carmel et al. and U.S.Pat. No. 5,483,855 to Julow et al. According to the method of the Carmelet al. patent, a crescent or wedge of material is preferably cut awayfrom an outer surface of the squealer band by a lathe during aneccentric turning process to produce a final balanced brake drum.According to the method of the Julow et al. patent, a circumferentiallyextending substantially constant depth cut is made along a portion ofthe squealer band by a milling machine to produce a final balanced brakedrum. Thus, it would be desirable to provide an improved structure for acomposite brake drum and method for producing such a brake drum which isrelatively simple and economical.

SUMMARY OF THE INVENTION

This invention relates to an improved structure for a composite brakedrum for use in a drum brake assembly and a method for producing such abrake drum. The composite brake drum includes a one-piece mountingflange and shell having a liner cast integrally in the shell portionthereof. The method for forming the composite brake drum of thisinvention includes the steps of: (a) providing a generally circularmetal blank having an initial pilot hole inner diameter; (b) spinforming the metal blank to produce a one-piece brake drum componentdefining a center longitudinal axis and including a cylindrical shellhaving a squealer band which defines a squealer band outer diameter, amounting flange extending radially inwardly from one end of the shelltoward the center longitudinal axis, and an annular lip extendingradially inwardly from an opposite end of the shell toward the centerlongitudinal axis, and wherein the shell, the flange, and the lipcooperate to define a cylindrical mold cavity; (c) subsequent to step(b), centrifugally casting a liner in situ within the mold cavity of thebrake drum component to thereby produce the composite vehicle brakedrum; and (d) subsequent to step (c), machining the initial pilot holeinner diameter to a final pilot hole inner diameter by locating off ofthe squealer band outer diameter.

Various objects and advantages of this invention will become apparent tothose skilled in the art from the following detailed description of thepreferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view, partially broken away, of a portion of aprior art heavy duty truck and trailer drum brake assembly.

FIG. 2 is a sectional view of a prior art brake drum illustrated in FIG.1.

FIG. 3 is a block diagram illustrating the sequence of steps forproducing the prior art brake drum illustrated in FIG. 2.

FIG. 4 is a sectional view similar to FIG. 2 of an alternate embodimentof a prior art brake drum.

FIG. 5 is a sectional view of an improved structure for a firstembodiment of a brake drum in accordance with this invention.

FIG. 6 is a sectional view of an improved structure for a secondembodiment of a brake drum in accordance with this invention.

FIG. 7 is a block diagram illustrating a first sequence of steps forproducing the brake drum of the present invention.

FIG. 8 is a cross sectional view showing the initial forming of theone-piece mounting flange and shell for the brake drum illustrated inFIG. 6

FIG. 9 is a cross sectional view showing the final forming of theone-piece mounting flange and shell for the brake drum illustrated inFIG. 6.

FIG. 10 is a block diagram illustrating a second sequence of steps forproducing the brake drum of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, there is illustrated in FIG. 5 a firstembodiment of a composite brake drum, indicated generally at 100, inaccordance with this invention. The brake drum 100 is associated with arear wheel of a vehicle and includes a one-piece mounting flange andshell, indicated generally at 62, and a liner 64. As will be discussedbelow, the one-piece mounting flange and shell 62 is preferably formedfrom steel and the liner 64 is preferably formed from gray cast iron.The liner 64 includes an inner surface 64A which is machined to define apredetermined braking surface.

The one-piece mounting flange and shell 62 defines a center longitudinalaxis X and includes a generally closed end or mounting flange portion66, a transition section 68, a generally axially extending cylindricalmain body 70, and an opened end 72 having an annular lip 72A. Thecylindrical body portion 70 defines an outer surface 70A and, in theillustrated embodiment, includes a raised continuously extending annularsquealer band 74. The cylindrical body portion 70 has a corrugatedsection which defines corrugation peak outer surface 70B, and acorrugation crest inner surface 70C. The corrugation peak outer surface70B defines a body outer diameter D2, and the corrugation crest innersurface defines a body inner diameter D3. The squealer band 74 includesan outer surface 74A which defines a squealer band outer diameter D. Fordiscussion purposes, the mounting flange portion 66 of the one-piecemounting flange and shell 62 includes the mounting flange 66, and theshell portion of the one-piece mounting flange and shell 62 includes aportion of the transition section 68 and the cylindrical main body 70.

The mounting flange portion 66 of the brake drum 100 includes agenerally centrally located pilot hole 66A formed therein and aplurality of lug bolt holes 66B (only one lug bolt hole 66B beingillustrated) spaced circumferentially around the pilot hole 66A. The lugbolt mounting holes 66B are adapted to receive wheel mounting studs (notshown) for securing a wheel (not shown) to the brake drum 100 forrotation therewith.

The mounting flange portion 66 defines a generally constant thicknessT3, and the transition section 68 defines a generally constant thicknessT4. The cylindrical body 70 defines a generally constant thickness T5,the squealer band 74 defines a generally constant thickness T6, and theopened end 72 defines a generally constant thickness T7. As will bediscussed below, in the illustrated embodiment the thicknesses T3 and T6are approximately equal to one another, and the thicknesses T4, T5, andT7 are approximately equal to one another and less than the thicknessesT3 and T6.

Referring now to FIG. 6, there is illustrated a second embodiment of acomposite brake drum, indicated generally at 100′, in accordance withthis invention. The brake drum 100′ is associated with a front wheel ofa vehicle and includes a one-piece mounting flange and shell, indicatedgenerally at 62′, and a liner 64′. As will be discussed below, theone-piece mounting flange and shell 62′ is preferably formed from steeland the liner 64′ is preferably formed from gray cast iron. The liner64′ includes an inner surface 64A′ which is machined to define apredetermined braking surface.

The one-piece mounting flange and shell 62′ defines a centerlongitudinal axis X′ and includes a generally closed end or mountingflange portion 66′, a transition section 68′, a generally axiallyextending cylindrical main body 70′, and an opened end 72′ having anannular lip 72A′. The cylindrical body portion 70′ defines an outersurface 70A′ and, in the illustrated embodiment, includes a raisedcontinuously extending annular squealer band 74′. The cylindrical bodyportion 70′ has a corrugated section which defines corrugation peakouter surface 70B′, and a corrugation crest inner surface 70C′. Thecorrugation peak outer surface 70B′ defines a body outer diameter D2′,and the corrugation crest inner surface defines a body inner diameterD3′. The squealer band 74′ includes an outer surface 74A′ which definesa squealer band outer diameter D′. For discussion purposes, the mountingflange portion 66′ of the one-piece mounting flange and shell 62′includes the mounting flange 66′, and the shell portion of the one-piecemounting flange and shell 62′ includes a portion of the transitionsection 68′ and the cylindrical main body 70′.

The mounting flange portion 66′ of the brake drum 100′ includes agenerally centrally located pilot hole 66A′ formed therein and aplurality of lug bolt holes 66B′ (only one lug bolt hole 66B′ beingillustrated) spaced circumferentially around the pilot hole 66A′. Thelug bolt mounting holes 66B′ are adapted to receive wheel mounting studs(not shown) for securing a wheel (not shown) to the brake drum 100′ forrotation therewith.

The mounting flange portion 66′ defines a generally constant thicknessT3′, and the transition section 68′ defines a generally constantthickness T4′. The cylindrical body 70′ defines a generally constantthickness T5′, the squealer band 74 defines a generally constantthickness T6, and the opened end 72′ defines a generally constantthickness T7′. As will be discussed below, in the illustrated embodimentthe thicknesses T3′ and T6′ are approximately equal to one another, andthe thicknesses T4′, T5′, and T7′ are approximately equal to one anotherand less than the thicknesses T3′ and T6′.

Turning now to FIG. 7, there is illustrated a block diagram of a firstsequence of steps for producing the composite brake drum 100, 100′ ofthis invention. Initially, in step 80, a flat sheet of suitablematerial, such as for example steel, is subjected to a stampingoperation to produce a generally flat circular blank having a roughpilot hole formed therein. Following this, in optional step 82, theblank is subjected to a stamping operation to produce a brake drumpreform having a desired profile. In particular, during optional step82, the mounting flange portion 66, 66′ of the respective brake drum100, 100′ can be formed to a desired profile.

Next, in step 84, the blank (shown in phantom at 102′ in FIG. 8) orpreform (not shown, if step 82 is performed), is supported in a suitablefixture, such as for example a well known mandrel-tailstock assembly,such as that indicated generally at 110 in FIG. 8, and is subjected toan initial forming process. During step 84, preferably a spinning tool104 is actuated and engages the material of the blank 102 as thespinning tool 104 is moved in the direction of the arrow S in order tospin form a partially formed one-piece mounting flange and shell 106′having a desired profile. In particular, during step 84, the spinningtool 104 makes multiple passes in order to form the desired profile ofthe partially formed one-piece mounting flange and shell 106′ of theassociated brake drum (FIG. 8 illustrating a partially formed one-piecemounting flange and shell 106′ which can be used to produce the brakedrum 100′ of this invention). Also, as illustrated and discussed below,during step 84 selected sections of the shell portion 106′ arepreferably thinned to predetermined tolerances.

Following this, the partially formed one-piece mounting flange and shell106′ is supported in a suitable fixture, such as for example amandrel-tailstock assembly, such as that indicated generally at 120 inFIG. 9, and is subjected to a final forming process in step 86. Duringstep 86, preferably a first flow forming tool 112 and a second flowforming tool 114 are actuated and move in the direction of arrows T andU, respectively, to engage the material of the partially formedone-piece mounting flange and shell 106′ in order to flow form thematerial thereof against the mandrel and produce a finished one-piecemounting flange and shell having a desired shell portion profile (FIG. 9showing the finished one-piece mounting flange and shell 62′ for used toproduce the brake drum 100′ of this invention).

As shown in FIG. 9, the illustrated mandrel-tailstock assembly 120 usedin the final forming process in step 86 includes an eccentric mandrel122. As shown therein, the mandrel 122 is operative enable the materialof the shell portion 106′ of the partially formed one-piece mountingflange and shell 106′ to be flow formed against a portion/side of themandrel, shown in FIG. 9 as flow forming the material against theportion/side of the mandrel 122 located in the upper half of thedrawing. Due to the profile of the illustrated one-piece mounting flangeand shell 62, 62′, namely due to the main body 70, 70′ provided with thecorrugations and the annular lip 72A, 72A′, both of which extendradially inwardly toward the axis X, X′ thereof, the mandrel 122 iseccentric to enable the finished one-piece mounting flange and shell 62,62′ to be removed from the mandrel-tailstock assembly 120 subsequent tostep 86. Alternatively, the mandrel-tailstock assembly 120 could beother than illustrated depending upon the structure of the finishedone-piece mounting flange and shell 62, 62′.

Next, in step 88, a gray iron liner 64, 64′ is cast in the shell portionof the respective one-piece mounting flange and shell 62, 62′.Preferably, the casting of the liner 64, 64′ is accomplished using acentrifugal casting process. However, other casting processes may beused as desired. After the casting of the liner 64. 64′, the mountingflange portion 66, 66′ of the brake drum is coined in step 90, and arespective pilot hole 66A, 66A′ is formed to a predetermined size alongwith the forming of the lug bolt mounting holes 66B, 66B′ during step92. Following this, the brake drum 100, 100′ is machined topredetermined tolerances during step 94. Next, in optional step 96, thebrake drum is subjected to a balancing operation to produce the finishedbrake drum 100, 100′.

Referring now to FIG. 9, there is illustrated a block diagram of asecond sequence of steps for producing the composite brake drum 100,100′ of this invention. Initially, in step 180, a flat sheet of suitablematerial, such as for example steel, is subjected to a laser cutting orstamping operation to produce a generally flat circular blank having apredetermined outer diameter and a predetermined inner diameter.Following this, in optional step 182, the blank is subjected to a metalforming operation, such as for example a stamping operation, to producea brake drum preform having a desired profile. In particular, duringoptional step 182, the mounting flange portion 66, 66′ of the respectivebrake drum 100, 100′ can be formed to a desired profile.

Next, in step 184, the blank (shown in phantom at 102′ in FIG. 8) orpreform (not shown, if step 82 is performed), is supported in a suitablefixture, such as for example a well known mandrel-tailstock assembly,such as that indicated generally at 110 in FIG. 8, and is subjected toan initial forming process. During step 184, preferably a spinning tool104 is actuated and engages the material of the blank 102 as thespinning tool 104 is moved in the direction of the arrow S in order tospin form a partially formed one-piece mounting flange and shell 106′having a desired profile. In particular, during step 184, the spinningtool 104 makes multiple passes in order to form the desired profile ofthe partially formed one-piece mounting flange and shell 106′ of theassociated brake drum (FIG. 8 illustrating a partially formed one-piecemounting flange and shell 106′ which can be used to produce the brakedrum 100′ of this invention). Also, as illustrated and discussed below,during step 184 selected sections of the shell portion 106′ arepreferably thinned to predetermined tolerances.

Following this, the partially formed one-piece mounting flange and shell106′ is supported in a suitable fixture, such as for example amandrel-tailstock assembly, such as that indicated generally at 120 inFIG. 9, and is subjected to a final forming process in step 186. Duringstep 186, preferably a first flow forming tool 112 and a second flowforming tool 114 are actuated and move in the direction of arrows T andU, respectively, to engage the material of the partially formedone-piece mounting flange and shell 106′ in order to flow form thematerial thereof against the mandrel and produce a finished one-piecemounting flange and shell having a desired shell portion profile (FIG. 9showing the finished one-piece mounting flange and shell 62′ for used toproduce the brake drum 100′ of this invention).

As shown in FIG. 9, the illustrated mandrel-tailstock assembly 120 usedin the final forming process in step 186 includes an eccentric mandrel122. As shown therein, the mandrel 122 is operative enable the materialof the shell portion 106′ of the partially formed one-piece mountingflange and shell 106′ to be flow formed against a portion/side of themandrel, shown in FIG. 9 as flow forming the material against theportion/side of the mandrel 122 located in the upper half of thedrawing. Due to the profile of the illustrated one-piece mounting flangeand shell 62, 62′, namely due to the main body 70, 70′ provided with thecorrugations and the annular lip 72A, 72A′, both of which extendradially inwardly toward the axis X, X′ thereof the mandrel 122 iseccentric to enable the finished one-piece mounting flange and shell 62,62′ to be removed from the mandrel-tailstock assembly 120 subsequent tostep 186. Alternatively, the mandrel-tailstock assembly 120 could beother than illustrated depending upon the structure of the finishedone-piece mounting flange and shell 62, 62′.

Next, in step 188, a gray iron liner 64, 64′ is cast in the shellportion of the respective one-piece mounting flange and shell 62, 62′.Preferably, the casting of the liner 64, 64′ is accomplished using acentrifugal casting process. However, other casting processes may beused as desired. After the casting of the liner 64. 64′, the mountingflange portion 66, 66′ of the brake drum is coined in step 190.

In step 192, the brake drum 100, 100′ is supported on a suitable fixture(not shown) and the respective liner surface 64, 64′ is machined todefine the predetermined brake surface 64A, 64A′ and the respectivepilot hole 66A, 66A′ is machined to define the predetermined innerdiameter D1, D1′. To accomplish this, the brake surface 64A, 64A ismachined to the predetermined size by locating off of the respectivesquealer band outer diameter D, D′, and the pilot hole 66A, 66A′ ismachined to the predetermined size by locating off of the respectivesquealer band outer diameter D, D1. Alternatively, the brake surface64A, 64A′, the pilot hole 66A, 66A′, or both the brake surface 64, 64A′and pilot hole 66A, 66A′, can be machined by locating off of a surfaceother than the squealer band outer diameter D, D1. For example, thebrake surface 64A, 64A′, the pilot hole 66A, 66A′, or both the brakesurface 64, 64A′ and pilot hole 66A, 66A′, can be machined by locatingoff of an outer surface of the shell 62, 62′ at some point other than atthe squealer band outer diameter D, D1. Such other outer surface of theshell 62, 62′ could be at the respective body outer diameter D2, D2′,and the respective body inner diameter D3, D3′, or at some pointtherebetween. Preferably, during step 192, the brake surface 64A and thepilot hole 66A of the brake drum 100 are machined by locating off of thesquealer band outer diameter D, and the brake surface 64A′ and the pilothole 66A′ of the brake drum 100′ are machined by locating off of thebody outer diameter D2′.

Following this, in step 194, the lug bolt mounting holes 66B, 66B′ areformed to a predetermined size by locating off of the pilot hole innerdiameter D1, D1′. Next, in optional step 196, the brake drum issubjected to a shot peening process, and in optional step 198, the brakedrum is subjected to a balancing operation to produce the finished brakedrum 100, 100′.

One advantage of this invention is that the brake drum 100, 100′includes a one-piece mounting flange and shell 62,62′ compared to theprior art composite brake drum 18 having a separate mounting flange 20and shell 22 which were welded together. Also, by forming the one-piecemounting flange and shell 62, 62′ of this invention by using a spinforming process, the thickness of one-piece mounting flange and shell62, 62′ can be varied along the length thereof and held to tighttolerances.

For example, when using a steel blank or preform having a thickness ofapproximately 0.25 inches, the spin forming process can be used toproduce a thickness T3 of approximately 0.25 inches in the mountingflange portion 66, 66′ a thickness T4 of approximately 0.19 inches inthe transition section 68, 68′ a thickness T5 of approximately 0.19 inthe cylindrical main body 70, 70′ a thickness T6 of approximately 0.25inches in the squealer band 74, 74′ and a thickness T7 of approximately0.19 inches in the opened end 72, 72′. In the prior art brake drum 18,because the mounting flange 20 and the shell 22 were formed by astamping and rolling process, respectively, it was not possible to thineither one of the flange 20 or shell 22 during the forming thereof.Also, using the spin forming process of step 84, 184 allows the squealerband 74, 74′ of the respective brake drum 100, 100′ to be formed of athickness which, if necessary, is sufficient to enable the brake drum100, 100′ to be balanced by removing material from the squealer band 74,74′ such as by the methods disclosed in the above Carmel et al. andJulow et al. patents.

Although the brake drum 100, 100′ of this invention has been describedand illustrated as forming the one-piece mounting flange and shell 62,62′ by using a series of spin forming operations followed by a finalflow forming operation, the one-piece mounting flange and shell 6262′can be formed using other metal forming processes. Also, although thebrake drum 100, 100′ of this invention has been described andillustrated in connection with a respective steel one-piece mountingflange and shell 62, 62′ and a gray cast iron liner 64, 64′, thesecomponents can be constructed from other metals. For example, theone-piece mounting flange and shell 62, 62′ can be formed from aluminumor alloys thereof, and the liner 64,64′ can be formed from nodular iron,austempered gray iron, or an aluminum composite material. In particular,the liner 64, 64′ may be cast from an aluminum based metal matrixcomposite (MMC). One particular MMC that can be used is an aluminumbased MMC containing silicon carbide particulate reinforcement. Such analuminum MMC is commercially available under the name DURALCAN, aregistered trademark of Alcan Aluminum Limited of San Diego, Calif.However, the base alloy of the MMC can comprise other alloys, such asfor example, magnesium, or titanium. Also, the particulate reinforcementmaterial can comprise other materials, such as for example, alumina,silicon nitride, graphite, or ceramics.

Also, the brake drum 100, 100′ of this invention can be other thanillustrated and described herein. For example, the brake drum 100, 100′can be an “integral hub” brake drum (not shown). In addition, althoughthe brake drum 100, 100′ of this invention has been described andillustrated in connection with the particular drum brake assemblydisclosed herein, the brake drum 100, 100′ can be used in connectionwith other kinds of vehicles and/or other drum brake assemblies. Forexample, this invention may be used in an automobile and a light ormedium duty truck, and/or in a “duo-servo” type of drum brake assembly(not shown), in a “dual mode” drum brake assembly (not shown), whereinthe service brake is of the leading/trailing type and the parking andemergency brake is of the duo-servo type, in a “drum-in-hat” disc brakeassembly (not shown), wherein the service brake is a disc brake and theparking and emergency brake is a drum brake.

In accordance with the provisions of the patents statues, the principleand mode of operation of this invention have been described andillustrated in its preferred embodiment However, it must be understoodthat the invention may be practiced otherwise than as specificallyexplained and illustrated without departing from the scope or spirit ofthe attached claims.

What is claimed is:
 1. A method for producing a composite vehicle brakedrum comprising the steps of: (a) providing a generally circular metalblank having an initial pilot hole inner diameter; (b) spin forming themetal blank to produce a one-piece brake drum component defining acenter longitudinal axis and including a cylindrical shell having asquealer band which defines a squealer band outer diameter, a mountingflange extending radially inwardly from one end of the shell toward thecenter longitudinal axis, and an annular lip extending radially inwardlyfrom an opposite end of the shell toward the center longitudinal axis,and wherein the shell, the flange, and the lip cooperate to define acylindrical mold cavity; (c) subsequent to step (b), centrifugallycasting a liner in situ within is the mold cavity of the brake drumcomponent to thereby produce the composite vehicle brake drum; and (d)subsequent to step (c), machining the initial pilot hole inner diameterto a final pilot hole inner diameter by locating off of the squealerband outer diameter.
 2. The method defined in claim 1 wherein subsequentto step (c), the step of coining the mounting flange.
 3. The methoddefined in claim 1 wherein subsequent to step (c), the step of forming aplurality of lug bolt mounting holes in the mounting flange by locatingoff of the final pilot hole inner diameter.
 4. The method defined inclaim 1 wherein step (d) includes machining an inner surface of theliner to a predetermined inner diameter to define a braking surfaceinner diameter by locating off of the squealer band outer diameter.
 5. Amethod for producing a composite vehicle brake drum comprising the stepsof: (a) providing a generally circular metal blank having an initialpilot hole inner diameter; (b) spin forming the metal blank to produce aone-piece brake drum component defining a center longitudinal axis andincluding a cylindrical shell which defines a shell diameter, a mountingflange extending radially inwardly from one end of the shell toward thecenter longitudinal axis, and an annular lip extending radially inwardlyfrom an opposite end of the shell toward the center longitudinal axis,and wherein the shell, the flange, and the lip cooperate to define acylindrical mold cavity; (c) subsequent to step (b), centrifugallycasting a liner in situ within the mold cavity of the brake drumcomponent to thereby produce the composite vehicle brake drum; and (d)subsequent to step (c), machining the initial pilot hole inner diameterto a final pilot hole inner diameter by locating off of the shelldiameter.
 6. The method defined in claim 5 wherein subsequent to step(c), the step of coining the mounting flange.
 7. The method defined inclaim 5 wherein subsequent to step (c), the step of forming a pluralityof lug bolt mounting holes in the mounting flange by locating off of thefinal pilot hole inner diameter.
 8. The method defined in claim 5wherein step (d) includes machining an inner surface of the liner to apredetermined inner diameter to define a braking surface inner diameterby locating off of the shell diameter.
 9. A method for producing aone-piece brake drum component adapted for use in a composite vehiclebrake drum comprising the steps of: (a) providing a generally circularmetal blank; (b) supporting the metal blank on a tool fixture having amandrel with an eccentric profile; and (c) spin forming the metal blankagainst the mandrel to produce a one-piece brake drum component defininga center longitudinal axis including a cylindrical shell and a mountingflange extending radially inwardly from one end of the shell toward thecenter longitudinal axis, the cylindrical shell having at least onecorrugation formed therein.
 10. The method according to claim 9 whereinthe one-piece brake drum component includes an annular lip extendingradially inwardly from an opposite end of the shell toward the centerlongitudinal axis.
 11. The method according to claim 10 wherein theshell, the flange, and the lip cooperate to define a cylindrical moldcavity; and wherein subsequent to step (c), the step of centrifugallycasting a liner in situ within the mold cavity of the brake drumcomponent to thereby produce the composite vehicle brake drum.
 12. Themethod defined in claim 11 including the step of machining the liner toform a braking surface.
 13. The method according to claim 9 furtherincluding moving a first spinning tool in a generally arcuate pathagainst the blank to partially form a one-piece mounting flange andshell prior to step (b).
 14. The method according to claim 13 whereinthe arcuate path is defined by the first spinning tool moving between atleast two operating positions with a first position defined by the firstspinning tool rotating about a first axis transverse to the centerlongitudinal axis and with the second position defined by the firstspinning tool rotating about a second axis generally parallel to thecenter longitudinal axis.
 15. The method according to claim 13 whereinstep (c) further includes a secondary spin forming process including thesteps of supporting the partially formed one-piece mounting flange andshell on the mandrel, moving a second spinning tool along a first linearpath, and moving a third spinning tool along a second linear path toproduce a finished one-piece mounting flange and shell.
 16. The methodaccording to claim 15 wherein first linear path is defined along a paththat extends traversely to the center longitudinal axis and the secondlinear path is defined along a path that is perpendicular to the centerlongitudinal axis.
 17. The method according to claim 9 furtherincluding: an initial spin forming process to produce a partially formedone-piece mounting flange, which includes the steps of supporting themetal blank on a first mandrel and moving at least a first spinning toolalong a first path to form the partially formed one-piece mountingflange and shell prior to step (b); and wherein step (c) furtherincludes a final spin forming process to produce a finished one-piecemounting flange and shell, which includes the steps of supporting thepartially formed one-piece mounting flange on the mandrel set forth instep (b) and moving at least a second spinning tool along a second pathto form the finished one-piece mounting flange and shell.
 18. The methodaccording to claim 17 wherein the first path is an arcuate path that isdefined by the first spinning tool moving between at least two operatingpositions with a first position defined by the first spinning toolrotating about a first axis transverse to the center longitudinal axisand with the second position defined by the first spinning tool rotatingabout a second axis generally parallel to the center longitudinal axis.19. The method according to claim 18 wherein the second path is a linearpath that is defined along a path that extends transversely to thecenter longitudinal axis.
 20. The method according to claim 19 includingthe step of moving a third spinning tool along a third path during thefinal spin forming process wherein the third path is a linear path isdefined along a path that is perpendicular to the center longitudinalaxis.
 21. The method according to claim 9 wherein step (c) furtherincludes forming the corrugation to have a common thickness with a mainbody portion of the cylindrical shell.
 22. A method for producing acomposite vehicle brake component comprising: (a) stamping apredetermined material into a circular blank; (b) spin forming the blankto partially form a one-piece mounting flange and shell; (c) flowforming the blank to form a finished one-piece mounting flange and shellhaving a squealer band defining a squealer band outer diameter; (d)centrifugally casting a linear in the shell; (e) forming a pilot hole toa predetermined size and coining the mounting flange; and (f) machiningthe one-piece mounting flange and shell to produce a finished brakecomponent including machining the pilot hole diameter by locating off ofthe squealer band outer diameter.
 23. The method defined in claim 22including the steps of forming a plurality of lug bolt mounting holes inthe mounting flange by locating off the pilot hole diameter.
 24. Themethod defined in claim 22 wherein step (b) further includes forming theone-piece mounting flange and shell to include a mounting flange portionat one end, an axially extending cylindrical main body portion at anopposite end, and a transition section interconnecting the mountingflange portion and the main body portion.
 25. The method defined inclaim 24 wherein step (d) further includes casting the liner on an innercylindrical surface of the main body portion to define a brakingsurface.
 26. A method for producing a composite vehicle brake componentcomprising: (a) stamping a predetermined material into a circular blank;(b) spin forming the blank to partially form a one-piece mounting flangeand shell including forming the one-piece mounting flange and shell tohave a mounting flange portion at one end, an axially extendingcylindrical main body portion at an opposite end, and a transitionsection interconnecting the mounting flange portion and the main bodyportion wherein the main body portion has a squealer band defining asquealer band outer diameter; (c) flow forming the blank to form afinished one-piece mounting flange and shell; (d) centrifugally castinga liner in the shell on an inner cylindrical surface of the main bodyportion to define a braking surface; (e) forming a pilot hole to apredetermined size; and (f) machining the one-piece mounting flange andshell to produce a finished brake component including machining thepilot hole and the braking surface by locating off of the squealer bandouter diameter.
 27. A method for producing a composite vehicle brakecomponent comprising: (a) stamping a predetermined material into acircular blank; (b) spin forming the blank to partially form a one-piecemounting flange and shell including forming the one-piece mountingflange and shell to have a mounting flange portion at one end, anaxially extending cylindrical main body portion at an opposite end, anda transition section interconnecting the mounting flange portion and themain body portion; (c) flow forming the blank to form a finishedone-piece mounting flange and shell; (d) centrifugally casting a linerin the shell on an inner cylindrical surface of the main body portion todefine a braking surface; (e) forming a pilot hole to a predeterminedsize; and (f) machining the one-piece mounting flange and shell toproduce a finished brake component including machining the pilot holeand the braking surface by locating off of the outer diameter of themain body portion during step (f).
 28. A method for producing acomposite vehicle brake component comprising: (a) stamping apredetermined material into a circular blank and supporting the blank ona first tool fixture; (b) spin forming the blank to partially form aone-piece mounting flange and shell; (c) supporting the blank oil asecond tool fixture having an eccentric mandrel and flow forming theblank to form a finished one-piece mounting flange and shell; (d)centrifugally casting a liner in the shell; (e) forming a pilot hole toa predetermined size; and (f) machining the one-piece mounting flangeand shell to produce a finished brake component.
 29. The method definedin claim 28 wherein step (c) further includes spin forming the blankagainst the eccentric mandrel to produce the one-piece mounting flangeand shell defining a center longitudinal axis with the mounting flangeextending radially inwardly from one end of the shell toward the centerlongitudinal axis.
 30. The method defined in claim 29 including the stepof forming at least one corrugation in the shell.
 31. The method definedin claim 30 including the step of forming an annular lip extendingradially inwardly from an opposite end of the shell toward the centerlongitudinal axis.
 32. The method defined in claim 31 wherein the shell,the flange, and the lip cooperate define a cylindrical mold cavity andstep (d) further includes centrifugally casting the liner within themold cavity.
 33. A method for producing a one-piece brake drum componentadapted for use in a composite vehicle brake drum comprising the stepsof: (a) providing a generally circular metal blank; (b) supporting themetal blank on a tool fixture having a mandrel; and (c) spin forming themetal blank against the mandrel to produce a one-piece brake drumcomponent defining a center longitudinal axis and including acylindrical shell and a mounting flange extending radially inwardly fromone end of the shell toward the center longitudinal axis, thecylindrical shell having at least one corrugation formed therein;wherein spin forming includes an initial spin forming process to producea partially formed one-piece mounting flange, which includes the stepsof supporting the metal blank on a first mandrel set forth in step (b)and moving at least a first spinning tool along a first path to form thepartially formed one-piece mounting flange and shell; and a final spinforming process to produce a finished one-piece mounting flange andshell, which includes the steps of supporting the partially formedone-piece mounting flange on a second mandrel and moving at least asecond spinning tool along a second path to form the finished one-piecemounting flange and shell wherein the first mandrel is a non-eccentricmandrel and the second mandrel is an eccentric mandrel.